This application relates to information transmission systems and, more specifically, to a system, method and apparatus for increasing the data rate on an existing repeatered telecommunication channel structure. An existing repeatered telecommunication channel structure which had been designed to operate at a specified data rate, transfers data at rates up to four times or more than the specified rate, after incorporating improved transceiver and repeater elements constructed and arranged in accordance with the invention into the system. The major benefits of having an increased data rate on an existing channel structure include a cost effective means for delivering new data services to customers on existing channel structures.
The use of telecommunication channel structures for high speed digital transmission of speech and data is essential for conducting everyday personal, business and governmental activities. As a result, costly high speed data services, such as the Integrated Services Digital Network (ISDN), have been developed to supplant conventional modems operating at substantially lower speeds than ISDN can provide. In addition, currently developing xDSL technologies will enable service providers to deliver digital service to customer sites at rates in excess of one megabit per second. Because of the increased demand for higher data rates at customer sites, there is a need to increase the data carrying capacity of service providers"" existing networks.
Several methods are being used and developed for increasing the data carrying capacity of service providers"" existing networks. For example, the use of fiber optics has increased significantly over the last 5 to 10 years. Further, HDSL2 technology (as described in a proposed draft ANSI standard T1E1.4/99-006R1) will enable the doubling of data rates over certain kinds of twisted-wire pairs. However, because of the cost and technical limitations associated with these and other extant methods for providing increased data carrying capacity, there remains a demand for increasing data rates on existing channel structures comprising cable bundles of twisted-wire pairs, optical fibers or coaxial cables, or the radio links of microwave systems.
The conventional repeatered T1-carrier system transfers data at the DS1 rate (1.544 Mbps) via a channel structure comprising cable bundles or sections of twisted-wire pairs connected between a first location, e.g., a central office, and a second location, e.g., a customer site. The cable sections of twisted-wire pairs are intended to interconnect a serial arrangement of repeaters, mounted in repeater equipment racks, between transceivers mounted in transceiver racks at the first and second locations. Typically, the transceiver racks and the repeater racks contain unpopulated printed circuit board or card slots reserved for the future installation of conventional DS1 rate T1-carrier transceivers and repeaters as required. In a typical T1-carrier installation, preselected twisted-wire pairs in the cable sections are reserved for connection in the future to such subsequently installed DS1 rate transceivers and repeaters.
The twisted-wire pair sections can include several gauges of wire, such as 19 AWG (American Wire Gauge), 22 AWG, 24 AWG, and 26 AWG. Each cable section typically has 25 or more twisted-wire pairs, preselected ones of which are reserved as spares or for connection to DS1 rate transceivers and repeaters installed in the future. A conventional repeatered T1-carrier system has a bit error ratio (BER) rate better than 1.0E-6 and preferably better than 1.0E-7. The design rules for a repeatered T1-carrier system are well known in the information transmission system art. See, for example, Engineering of T1 Carrier System Repeatered Lines, by H. Cravis and T. V. Crater, Bell System Technical Journal, March 1963, 431-486 and Subscriber Loop Signaling and Transmission Handbook, Digital, by Whitham D. Reeve, IEEE Press, 1995 (xe2x80x9cReevexe2x80x9d).
When the repeatered T1-carrier system was designed, however, it was generally accepted that technology limited the rate for digital transmission over the required distances and conditions of the T-1 carrier channel structure to the DS1 rate. If transmission was required at a higher data rate, for example DS2 (6.312 Mbps), it was generally known and accepted that a channel structure different from the T-1 carrier channel structure was required; see for example Table 1-1 of the above-cited text by Reeve and the T2-carrier publications identified in the IDS submitted with this application. The existing channel structure for repeatered T-1 carrier currently supports only the DS1 rate.
Because new data transfer applications demand an increase in data bandwidth over a limited number of twisted-wire pairs, it is desirable for a service provider having the channel structure of a repeatered T1-carrier system to increase the data rate over that channel structure. However, any changes made to the repeatered T1-carrier system to provide an increased data rate must not cause unacceptable degradation of any existing services or an unacceptable amount of crosstalk coupled to neighboring twisted-wire pairs providing the same or other services. Any modification of an existing T1-carrier system to increase the data rate over the T1-carrier channel structure must be easy to implement, must provide equal or improved performance compared to the existing system, and must provide all the operation and maintenance features and safeguards required by the service provider.
A need exists to increase the data rates over existing telecommunication channel structures, such as the repeatered T1-carrier channel structure. The system for increasing the data rate must be cost effective and compatible with existing services.
It is therefore a principal object of the present invention to provide the capability of substantially increasing the data transfer rate over an established or existing channel structure above and beyond the established data transfer rate of the established channel structure, without modification of the channel structure.
The principal object is achieved by equipping the channel structure with one or more transceivers and one or more repeaters that are operational at the substantially increased data transfer rate, without modification of the established channel structure.
In one aspect of the present invention, the principal object is achieved by equipping unpopulated equipment rack slots, which have been reserved for future installation of transceivers and repeaters operational at the established data transfer rate, with transceivers and repeaters operational at the substantially increased data transfer rate.
In another aspect of the present invention, the principal object is achieved by the one-for-one replacement of extant transceivers and repeaters with transceivers and repeaters operational at the substantially increased data transfer rate.
In yet another aspect of the present invention, the principal object is achieved by both equipping unpopulated equipment rack slots, which have been reserved for future installation of transceivers and repeaters operational at the established data transfer rate, with transceivers and repeaters operational at the substantially increased data transfer rate, and also by the one-for-one replacement of extant transceivers and repeaters with transceivers and repeaters operational at the substantially increased data transfer rate.
Still another object of the present invention to provide a telecommunication system that substantially overcomes the data transfer rate limitations imposed on conventional repeatered T1-carrier systems using existing T1-carrier channel structure.
It is a further object of the present invention to increase the data transfer rate in a conventional repeatered T1-carrier system by a substantial amount, e.g., by a factor of two or more, to assist a service provider to satisfy customer demand for new data services on existing repeatered T1-carrier channel structures.
Yet another object of the present invention is to incorporate new coding and modulation procedures into existing repeatered T1-carrier systems by designing replacement transceivers and repeaters, which embody the new procedures and are capable of providing data transfer rates substantially higher than the DS1 rate used on existing T1-carrier channel structure.
Still another object of the present invention is to provide improved digital transmission over an existing repeatered T1-channel structure by using components constructed in accord with the invention that are spectrally compatible with the existing system and do not interfere with or cause degradation of existing services.
A further object of the present invention is to provide a remote means for testing each component of the system constructed in accordance with the invention, in order to satisfy the operating and maintenance requirements of the service provider.
In accordance with our invention, we provide a method for increasing the rate of digital transmission over the repeatered channel structure of an existing telecommunication system having at least one transceiver connected at each end of the structure and at least one repeater incorporated into the structure, wherein the system was initially designed to transmit data at a first data rate. The method includes the step of equipping the system with transceivers that are operational at a data transfer rate, substantially higher than the established data transfer rate for the system, and that are spectrally compatible with the existing transceivers. The method further includes the step of equipping the system with one or more repeaters that are operational at the substantially higher data transfer rate and that are spectrally compatible with the existing repeaters.
To generate the required signal at the higher data rate, we provide a method which further includes the step of transmitting a transmit signal from the higher transfer rate transceiver at one end of the channel structure in response to an input data stream having the higher transfer rate; the step of regenerating the transmit signal at each of the higher transfer rate repeaters; the step of acquiring a signal representative of the transmit signal at the higher transfer rate transceiver located at the other end of the channel structure; and the step of generating from the acquired signal an output data stream having the higher transfer rate and being a time delayed version of the input data stream.